Wire mesh thermal radiative element and use in a radiative oven
View Patent ↗A high speed cooking apparatus employing a low voltage high current system for heating foods employing a novel wire mesh heating element. The system herein described providing the benefits of high speed cooking like that further described by U.S. Provisional Application 60/822,028 filed on Aug. 10, 2006, but yet providing significant cost benefit and simplicity over said system.
1. A radiant oven comprising:
a heating cavity configured to receive a load to be heated;
a heating element having a radiative black body area sized and positioned to heat the load; and
a power supply to supply power to the heating element,
wherein a ratio of a resistance of the heating element to the radiative black body area of the heating element is less than 2 ohms/m 2 and the heating element is capable of reaching about 1400 Kelvin from room temperature in less than 10.3 seconds.
2. The radiant oven of claim 1 , wherein the radiative black body area is over 0.25 m 2 .
3. The radiant oven of claim 1 , wherein the ratio is approximately 0.1137 ohms/m 2 .
4. The radiant oven of claim 1 , wherein the heating element comprises a wire.
5. The radiant oven of claim 1 , wherein the heating element has a specific heat capacity of less than 0.36 KWH of energy for raising the temperature of the heat element from room temperature to about 1400° K, wherein an equation relating a heat energy to the specific heat capacity, where the unit quantity is in terms of mass is:
Δ Q=mcΔT
where ΔQ is the heat energy put into or taken out of the element (where P×time=ΔQ), m is the mass of the element, c is the specific heat capacity, and ΔT is the temperature differential where the initial temperature is subtracted from the final temperature.
6. The radiant oven of claim 1 , further comprising a relay for cycling the power to the heating element, and a control circuit for controlling the relay.
7. The radiant oven of claim 1 , wherein the radiative black body area of the heating element is movable relative to the load.
8. The radiant oven of claim 1 , wherein a distance between the load and the radiative black body area of the heater is not less than one half of an inch.
9. The radiant oven of claim 1 , further comprising a tray configured to support the load, the tray being movably attached to a chassis of the radiant oven for adjusting the distance of the tray from the radiative black body area of the heating element.
10. The radiant oven of claim 1 , further comprising an oven door and a reflector disposed on or in the oven door for reflecting radiation.
11. The radiant oven of claim 1 , wherein the heating element comprises multiple heating elements, the multiple heating elements share a first bus and a second bus, the first bus is in electrical communication with a positive voltage of the power supply and the second bus is in electrical communication with a negative voltage of the power supply.
12. The radiant oven of claim 1 , further comprising a control circuit configured to monitor a condition of the load by measuring one or more of: a color of the load, a moisture level of a surface of the load, and a moisture level of air in the oven.
13. The radiant oven of claim 1 , wherein the power supply supplies a DC voltage to the heating element.
14. The radiant oven of claim 12 , wherein the DC voltage is less than 24 Volts.
15. The radiant oven of claim 1 , wherein the power supply comprises a low voltage high current system.
16. The radiant oven of claim 1 , wherein the heating element has a combined resistance of less than 10 ohms.
17. The radiant oven of claim 1 , wherein the heating element comprises a wire having a thickness less than or equal to 1 mm.
18. The radiant oven of claim 1 , wherein the heating element comprises a wire mesh cloth.
19. A heating method comprising:
heating a cavity configured for receiving a load using a heating element sized and positioned to heat the load; and
discharging current from a power supply through the heating element,
wherein a ratio of a resistance of the heating element to the radiative black body area of the heating element is less than 2 ohms/m 2 and the heating element is capable of reaching about 1400 Kelvin from room temperature in less than 10.3 seconds.
20. The heating method of claim 19 , wherein the radiative black body area is over 0.25 m 2 .
21. The heating method of claim 19 , wherein the ratio is approximately 0.1137 ohms/m 2 .
22. The heating method of claim 19 , wherein the heating element has a specific heat capacity of less than 0.36 KWH of energy for raising the temperature of the heat element from room temperature to about 1400° K, wherein an equation relating a heat energy to the specific heat capacity, where the unit quantity is in terms of mass is:
Δ Q=mcΔT
where ΔQ is the heat energy put into or taken out of the element (where P×time=ΔQ), m is the mass of the element, c is the specific heat capacity, and ΔT is the temperature differential where the initial temperature is subtracted from the final temperature.
23. The heating method of claim 19 , further comprising cycling the power to the heating element.
24. The heating method of claim 19 , further comprising moving the radiative black body area of the heating element relative to the load.
25. The heating method of claim 19 , further comprising monitoring a condition of the load by measuring one or more of: a color of the load, a moisture level of a surface of the load, and a moisture level of air in the oven.
26. The heating method of claim 19 , wherein the power supply comprises a low voltage high current system.
27. The heating method of claim 19 , wherein the heating element has a combined resistance of less than 10 ohms.
28. The heating method of claim 19 , wherein the heating element comprises a wire having a thickness less than or equal to 1 mm.